Antibiotics are widely used in both animals and humans to treat bacterial infection. This use (and often overuse) has caused bacteria to evolve and develop resistances against the treatment, posing great risks for human health globally.
The World Health Organization (WHO) identifies climate change as a key factor in transmitting infectious diseases worldwide. A recent study published in the journal Nature Climate Change on 21 May 2018 found a connection between temperature and antibiotic resistance. Led by Derek MacFadden from the University of Toronto (Canada), him and other researchers examined the distribution of antibiotic resistance across the United States and tried to find explanations for the varying rates across the country.
The authors linked data of antibiotic resistance to local climate data and other variables, such as population density or local prescribing rates. The final database included medical information from 223 facilities across 41 states between 2013 and 2015. Using different computer models, they found that an increase in minimum temperature was associated with a rise in antibiotic resistance. This was the case for the majority of tested antibiotics and bacteria types. In other words, significantly warmer regions had a higher proportion of antibiotic resistance. The researchers also tested other variables that affect the temperature-resistance relation. Indeed, there was a linkage between population density and resistance rates, which may be explained by higher transmission rates in densely populated areas. Other than that, they did not find any more factors that influenced the relationship between antibiotic resistance and temperature.
It is important to note that correlation does not directly imply causation. MacFadden and colleagues give a few suggestions on why antibiotic resistance is associated with higher temperatures. For example, higher temperatures may allow the spread of resistance genes through the so-called horizontal gene transfer (this is the transferal of genetic information between organisms), therefore this and other hypotheses need to be tested in the future.
Human health and climate change are major concerns driving the field of medical and environmental research forward. This study provides an important insight into possible effects of higher temperatures on antibiotic resistance. Future research will show whether these findings are applicable to different countries and ultimately across continents.